medium with matched refractive indices of the solid and liquid phases. The planar laser-
induced fluorescence (PLIF) technique described is the first to simultaneously visualize the
3D pore-scale flow of two immiscible liquid phases in porous media. Through the application
of a highly precise index matching method and the employment of up-to-date CCD imaging
hardware, the system features a high spatial resolution and sampling rate. The method was …